ENG-4367 Demo Dashboard instructions

- replaced instructions to open a terminal window and run the "launch
voter" script with instructions to open two terminal windows
and run "./run.sh" and ".run.sh client".
- same for voltkv
- updated links to documentation on voltdb.com
- removed "Getting Started" tab which didn't render correctly and linked to Getting Started, there are already several other links to the documentation page.
- Made "Next Steps" the last page.
- removed "Cool Tools" tab.  This page/tab was fluff.  Added instructions for using VoltDB Studio and SQLCMD within the Voter and VoltKV instructions.  "Next Steps" is a more logical end point.
- removed launch script (no longer used in instructions).  The launch script only worked on a Mac or a GNOME-based linux.  KDE users ran into issues for no good reason, it made a bad first impression, and there were no instructions for what to do if you didn't have GNOME.